TDF
I think that's a great idea and if you have the time and patience, it's a great endeavor.
have him do whatever is simple and can make money. submitting to TGP's is a great way to start, or doing graphics or gateway pages or anything. pay him 50% of what he makes and he gets to learn for free and it won't cost you anything either. have him do little things to help you out to teach him the ropes and keep you moving forward on your projects at the same time.
I've started many people this way and it definitely comes around. First of all, I enjoy teaching what I know, plus after 6 months to a year, they'll have a solid foundation upon which they can learn programming, advanced design or administration skills and then start teaching you things you didn't know!
If they ever leave, then that's okay too, I have lots of people whom i trained from scratch working for big companies around the country now and it's a very valuable resource for questions or subcontract help or industry insight or VIP passes or whatever. Plus i still have residual checks coming in from the work they did for me 4 years ago
I say teach everything you know, it's tough enough an industry as it is, the more educated we all are and the more of us there are, the more we can all work together and all make more money.